Conversion Rate in Analytics

Hi!

I feel awful even saying the words "Conversion Rate", but I'm going to go there anyway lol. We used to have a report that followed our in-house definition of  Conversion Rate, but it might not be accurate anymore and the person who made it isn't here anymore. Additionally we would LOVE for this to be a self updating widget in Analytics if possible. Since people can't buy a membership and tickets in the same transaction online we widened out definition of "Converted" to people who bought a membership and tickets in the same day/all the people who bought any tickets. Our rationale is that they had a choice to buy full price tickets and no membership, or buy a membership and tickets. Even those who are renewing have that option so we include them too, not just non members. 

I know that this mixes Membership and Seats & Tickets data, but I thought maybe I could cobble something together with the data options that cross over into other areas. I have my eye on Campaign Category in the Membership cube. I have categories for Admissions and then two for our Membership categories? What I'm unsure of is how to I ask for when that happens on the same day. 

Likely I won't be able to get to the data I want, but I thought I'd drop a line in the water here and see what I come up with.

Jenny